Preformed stainless steel crowns (SSCs) are still the preferred choice for whole or partial replacements of teeth. They are a very durable and reliable restoration for a tooth in need of complete coverage. Typically, stainless steel crowns are designed to provide long-term coverage of primary molar teeth and long-term provisional coverage of first permanent molar teeth.
Commercially available stainless steel crowns are preformed into an anatomically correct shape having a life-like height, contour, and occlusal surface. Dental composites provide an alternative, which resemble teeth, but lack the strength of preformed stainless steel crowns. Many patients, such as those with extensive caries, or those who have occlusions with deep anterior bites, or those who grind their teeth, generally need the strength of stainless steel crowns.
Stainless steel crowns are also desirable because they are made of a malleable material that allows the crown to be cut and trimmed to provide a comfortable bite on the occlusal surface of the opposite tooth. Furthermore, stainless steel crowns can be crimped around the base of the remaining portion of the tooth to provide a smooth, comfortable and secure fit.
Stainless steel crowns, however, have an unattractive appearance. Thus, there is a need for stainless steel dental crowns that have a more natural look with preferably a tooth-like color. Attempts have been made using resins, such as polyesters, epoxies, acrylics, and high-density polyethylene, to form an aesthetically pleasing veneer. Some veneers require the use of mechanical retention means, such as a screen mesh, on the facial side of a tooth as a foundation to which is attached the veneer. However, there is still a need for more durable aesthetic SSCs.
An aesthetic SSC is designed with several objectives in mind. One purpose is to hide the base material covering the natural tooth so that a more natural looking artificial tooth is seen. The aesthetic SSC also makes contact with other teeth or dental work, as well as food items placed in the mouth. Consequently, the preformed crown with the veneer or coating in place must be able to withstand great shearing stresses because of the contact with forces of occlusion.